An incandescent light bulb 10 as shown in FIG. 1 is an electric lamp that produces light by heating a filament wire 12 typically made of tungsten to a high temperature by passing an electric current through it. The hot filament 12 is protected from oxidation with a glass or quartz bulb 14 that is filled with inert gas or evacuated. The light bulb 10 is supplied with electrical current by terminals 16 in the glass. Most bulbs are mounted in a socket 18 to provide mechanical support, electrical connections and a standard by which it may be easily used in many applications. The most commonly used light bulb for general purpose lighting is the A19 bulb where the term “A19” encodes the width of the bulb at its widest point. The socket of the “A19” bulb is typically an Edison socket which includes a conventional screw base. The incandescent lamp is widely used in consumer and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting.
However, incandescent bulbs are much less efficient than most other types of lighting; most incandescent bulbs convert less than 5% of the energy they use into visible light whereas the remaining energy is converted into heat. The luminous efficacy of a typical incandescent bulb is 16 lumens per watt, compared to a range of 46 to 200 lm/W of a light-emitting diode (LED) lamp. Incandescent bulbs also have short lifetimes compared with other types of lighting; around 1000 hours for home light bulbs versus a range of 25,000 to 100,000 hours for LED lamps. Because of these inefficiencies, incandescent light bulbs are gradually being replaced in many applications by other types of electric lights, such as fluorescent lamps, compact fluorescent lamps (CFL), cold cathode fluorescent lamps (CCFL), high-intensity discharge lamps, and light-emitting diode lamps (LED). Some jurisdictions, such as the European Union, are in the process of phasing out the use of incandescent light bulbs.
FIG. 2 illustrates a typical LED-based lighting device 20 using an LED module 22 for replacing the standard A19 incandescent light bulb comprising a light lens 24, a heat sink and power supply enclosure 26 and an Edison socket 28. The LED module 22 that is used in LED-based lighting devices 20 predominately provides a Lambertian distribution. Because LEDs do not emit light in all directions, the directional characteristic of the output light is a major design consideration for LED lamps.
US20110215707 entitled “Constrained Folded Path Resonant White Light Scintillator” discloses an optical emitter 30 that can enable a more efficient disbursement of light by a light source such as an LED. Referring now to FIG. 3, (copy of FIG. 1 of patent application Ser. No. 12/716,337 entitled “Constrained Folded Path Resonant White Light Scintillator”), the optical emitter 30 includes a first conic reflector 32 that further includes an optical element 38 for defining an aperture for passing light into the optical emitter 30 from an LED. The optical emitter 30 includes a second conic reflector 34 opposite the first reflector 32 for collimating light admitted through the aperture. A volumetric light conversion element 36 between the first and second reflectors converts light from a first wavelength to a second, longer wavelength and then emits the converted light. The light conversion element 36 is substantially solid and includes an annular outer surface 37 through which light emits from the optical emitter 30 in a generally toroidal pattern. The light conversion element 36 can include phosphor dispersed in resin.
FIG. 4 illustrates the optical emitter 30 of FIG. 3 mounted on an LED-based lighting device 40 similar to that shown in FIG. 2. The optical emitter 30, along with a light lens 24, a heat sink and power supply enclosure 26 and an Edison socket 28 provide an alternative to the standard A19 incandescent light bulb. The subsequent distribution of light (i.e. the toroidal distribution) emitted from the optical emitter 30 may be less focused and more evenly distributed spherically than that of a typical LED-based lamp.